[PATCH v6 net-next 14/14] tcp: accecn: enable AccECN

chia-yu.chang
2025-11-14T07:14:24Z

Enable Accurate ECN negotiation and request for incoming and
outgoing connection by setting sysctl_tcp_ecn:

+==============+===========================================+
| | Highest ECN variant (Accurate ECN, ECN, |
| tcp_ecn | or no ECN) to be negotiated & requested |
| +---------------------+---------------------+
| | Incoming connection | Outgoing connection |
+==============+=====================+=====================+
| 0 | No ECN | No ECN |
| 1 | ECN | ECN |
| 2 | ECN | No ECN |
+--------------+---------------------+---------------------+
| 3 | Accurate ECN | Accurate ECN |
| 4 | Accurate ECN | ECN |
| 5 | Accurate ECN | No ECN |
+==============+=====================+=====================+

Refer Documentation/networking/ip-sysctl.rst for more details.

Signed-off-by: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
---
net/ipv4/sysctl_net_ipv4.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index ef21a85e021c..bde49331dc07 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -47,7 +47,7 @@ static unsigned int udp_child_hash_entries_max = UDP_HTABLE_SIZE_MAX;
static int tcp_plb_max_rounds = 31;
static int tcp_plb_max_cong_thresh = 256;
static unsigned int tcp_tw_reuse_delay_max = TCP_PAWS_MSL * MSEC_PER_SEC;
-static int tcp_ecn_mode_max = 2;
+static int tcp_ecn_mode_max = 5;
static u32 icmp_errors_extension_mask_all =
GENMASK_U8(ICMP_ERR_EXT_COUNT - 1, 0);

--
2.34.1